Opponents of President Donald Trump's decision
to scrap his predecessor's climate change
policies say they will organise a public campaign
and pursue legal avenues to challenge it.
California and New York issued a joint statement
saying they would continue the fight against
climate change.
Environmental groups have hired a host of
lawyers to challenge Mr Trump's move that
boosts fossil fuel production.
Mr Trump said he wanted to end "job-killing
regulations".
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His supporters believe that ending the climate
change rules brought in by Barack Obama will
create thousands of jobs in the gas, coal and oil
industries.
The governors of New York and California
summed up opponents' views by saying Mr
Trump's stance was "profoundly misguided and
shockingly ignores basic science".
In a joint statement, Governors Jerry Brown of
California and Andrew Cuomo of New York, both
Democrats, said: "With or without Washington,
we will work with our partners throughout the
world to aggressively fight climate change and
protect our future."
The two states have set even stricter targets on
reducing greenhouse gas emissions than required
by Mr Obama's rules and have far-reaching plans
for converting to renewable energy sources for
producing electricity.
Governor Brown said: "Erasing climate change
may take place in Donald Trump's mind, but
nowhere else."
A host of legal issues could be in the pipeline.
California has a special waiver allowing it to
enforce tougher measures on vehicle emissions.
Mr Trump could rescind that - but this would
lead to a fierce challenge.
He could also ask Congress to revoke the Clean
Air Act.
Back in 2007, the US Supreme Court ruled that
carbon dioxide gas was a pollutant under the
Act.
Some experts believe that the ultimate goal of
Mr Trump's executive order is to overturn that
ruling.
'High hurdle'
Already tied up in the courts is Mr Obama's
Clean Power Plan (CPP), which seeks to cut
fossil fuels from electricity production.
The BBC's environment correspondent, Matt
McGrath, says Mr Trump will let the CPP fester
there while coming up with a much weaker
replacement.
David Goldston, of the Natural Resources
Defence Council, said activists were gearing up
for legal challenges.
He said: "The president doesn't get to simply
rewrite safeguards; they have to... prove the
changes are in line with the law and science. I
think that's going to be a high hurdle for them."
Any legal challenges would dovetail with action
to win over public opinion.
Jeremy Symons, of the Environmental Defence
Fund, told Associated Press: "In terms of the big
picture, our strategy is simple: shine a spotlight
on what is going on and mobilise the public
against these rollbacks."
But Mr Trump's move does have supporters.
US Chamber of Commerce president Thomas
Donohue said: "These executive actions are a
welcome departure from the previous
administration's strategy of making energy more
expensive through costly, job-killing regulations
that choked our economy."
Mr Trump's Energy Independence Executive
Order suspends more than half a dozen
measures enacted by his predecessor.
Although during his election campaign he also
vowed to pull the US out of the Paris climate
deal agreed in December 2015, he has not
spelled out the US intentions.
Whatever the US chooses, the EU, India and
China say they will stick to their pledges made in
Paris.
On Wednesday, Chinese foreign ministry
spokesman Lu Kang said: "No matter how other
countries' policies change, as a responsible large
developing country, China's resolve, aims and
policy moves in dealing with climate change will
not."